Margaret is Bird's mother and a secondary protagonist in *Our Missing Hearts*. She is a poet and activist who becomes a symbol of resistance against the oppressive PACT policies. Her strong desire to combat societal injustices leads her to make significant sacrifices, including leaving her family to protect them.

Sadie is a 12-year-old schoolmate of Bird in *Our Missing Hearts*. She is separated from her parents due to PACT and resides in foster care, driven by the hope of reuniting with them. Sadie plays a crucial role in Bird's journey by revealing the truth about his mother’s activism and offering him friendship and support.

Domi is a college friend of Margaret in *Our Missing Hearts*. Despite her wealth, she supports the underground librarian movement by providing refuge for Margaret, Sadie, and Bird. Her commitment to activism remains strong, utilizing her resources to assist the cause.

Ethan is Bird’s father and Margaret’s husband in *Our Missing Hearts*. As a linguist, Ethan values language and plays a key role in keeping Bird safe while navigating the societal challenges posed by PACT. His love for his family is evident, although his choices sometimes inadvertently push Bird to seek the truth on his own.